3:16, Carnage Amongst The Stars, brings to mind the book Starship Troopers. On a first read, you might think of the movie version, but racking up kill totals is only the start of the game. The moral ambiguity and hard choices present in the book can all come up in the middle to late stages of a 3:16 campaign.
The Setting
Humans have turned Earth into a utopia, where nobody needs to die until they're too bored to live. The first encounter with aliens shows that Earth is vulnerable to threats from space, and so the military decides on a first strike policy. Travel to alien home worlds and eliminate the threat at the source (often before it even becomes a threat).
Ostensibly, it's a game about killing.
Character Creation
Character creation is pretty simple, and yields a character who is only slightly more than one-dimensional. You put ranks into only two abilities: Fighting Ability, and Non-Fighting Ability. Every challenge in the game comes down to using the most appropriate of those abilities.
The only bit that keeps your character from initially being entirely one-dimensional is picking a phrase that is their Reputation. This hints at the character growth that can come later.
You'd be forgiven for thinking, at this point, that the game was little more than an excuse to roll dice and kill aliens. That's part of it, but not the main part.
Killing Aliens
Let's get this part out of the way. Every mission is all about removing the alien threat from a planet. What the threat is and how it's removed is up to the GM, but the mechanics are the same. The planet has a number of Threat tokens associated with it, and PCs remove those threat tokens through encounters.
Combat in the game is not tactical, but abstract. In Starship Troopers there wasn't much in the way of tactical combat, just mowing down the enemy. In 3:16, you roll dice to see how many enemy you kill whenever you remove a threat token. There are some tactics involved, based on the range of your weapons and your movement into different ranges.
But the combat is just an excuse for interesting character development.
Character Development
These characters start out nearly one-dimensional, and are fleshed out during play. They start out with access to one Strength and one Weakness, and gain access to more as they gain in experience.
Using a Strength in an encounter allows a player to narrate a brief flashback that tells how their character gained a particular strength. It might be "Strength of Will", "Ferocious When Cornered", "Meek Until Threatened", etc. The player will choose a phrase describing that Strength.
When a player uses a Strength, the current encounter ends in a victory for the PCs.
Using a Weakness also allows a narration that gives more insight into the character. In this case, though, the weakness isn't something that helps the character. When using a Weakness, that player is removed from the encounter and has failed in some way. One threat token is also removed, but the encounter goes on for everyone else.
It's the act of using Strengths and Weaknesses in encounters that builds these characters into three-dimensional beings. We get to know them better through the rigors of battle.
Over time, the characters also rise in rank, getting more responsibility in the fleet. Eventually, someone will become a Colonel, and get to decide which planets are targeted. That player then takes over part of the roll of the GM, in deciding what sort of aliens are encountered next.
Ultimately, one of them might become the Brigadier, in charge of everything. After that, what the fleet does is up to that character.
The machinations of the character to get to those exalted ranks, and to resolve personal grudges that come up during play, become more and more the focus of the stories.
Overall
3:16 is a beautiful game. It starts in simplicity, and allows characters to grow during play. It models faceless troopers turning into real people through the stress of shared battles. It allows combat to be resolved quickly, without turning into a tactical quagmire.
That said, it is a game about killing aliens, and hard moral choices. Definitely not for everyone, but if it sounds in the least interesting, get it.
The PDF version is only $10 as of this writing from DriveThruRPG.

